Manure-breeding muscid flies, particularly the house fly, Musca domestica, and occasionally the little house fly, Fannia canicularis, and the black garbage fly, Hydrotaea aenescens, are a serious problem for poultry producers in the northeastern United States. Other flies commonly associated with northeastern poultry operations, but rarely noticed, are small dung flies of the family Sphaeroceridae.
Fly populations may create a public health nuisance around the farm and in nearby communities, resulting in poor community relations and threats of litigation. House flies can transmit more than 100 human and animal-disease-causing organisms, including protozoa, bacteria, viruses, rickettsia, fungi, and worms. House flies are considered intermediate hosts for tapeworms and may transmit ascarids (parasitic roundworms) to caged birds. Flies carry ascarid and other nematode eggs on their feet from manure to pens, feed, and water. Fly maggots ingest tapeworm and ascarid eggs from the poultry manure and retain them in the gut until maturity. In turn, infected flies are ingested by the feeding bird. Although it appears that avian influenza is spread principally by contaminated shoes, clothes, and equipment, the virus has been isolated from adult house flies.
Current pest control measures often rely on pesticides to keep pest populations below economic injury levels or nuisance thresholds. Since these thresholds are not well defined, control practices are generally carried out when the pests are observed on the birds or in the poultry house. Extensive or improper use of pesticides can result in the extermination of biological control agents and the development of pesticide resistance. It can also create harmful and illegal residues in meat and eggs and can contaminate the environment. Destruction of biological control agents and pesticide resistance results in larger pest populations, increased pesticide use, and higher control costs.
Besides flies, beetles, and mites, several beneficial insects and mites are often associated with accumulations of poultry manure. Predaceous arthropods such as mites, hister beetles, and parasitic wasps are all important biological control agents in suppressing fly populations. Proper cultural practices encourage poultry manure accumulations containing large populations of beneficial predators and parasites that can suppress house fly populations. In the Northeast, macrochelid mites and hister beetles are the major predators in caged-layer operations.
The macrochelid mite, Macrocheles muscaedomesticae, is the most common mite in poultry manure. The reddish brown mite, slightly less than 1/16 inch in size, feeds on house fly eggs and first-instar larvae. It can consume up to 36 house fly immatures per day. Mites are found on the outermost layer of the manure, particularly its peak. Macrochelids can cause substantial reductions in house fly numbers, but large mite populations are required for any appreciable impact.
The principal hister beetle in northeastern poultry houses is Carcinops pumilio, a small black beetle, approximately 1/8 inch long. It feeds on house fly eggs and first-instar larvae. Adult and immature hister beetles live in the surface layers of manure and forage for fly and mite prey. Each adult destroys an average of 54 housefly immatures per day at 80.degree. F. Predation declines to 12 per day at 59.degree. F., and increases to 83 per day at the higher temperature of 91.degree. F. Starved beetles can consume as many as 104 immatures per day. Well-fed females lay up to 10 eggs per day, and live over 3 months. Hister beetles also consume all immature stages of the tiny dung flies (Sphaeroceridae) that occasionally break out at manure heaps.
For a more complete discussion of the control of pests in poultry barns, see "Pest Management Recommendations for Poultry" Donald A. Rutz & Charles W. Pitts, 1993, Cornell University/Penn State Cooperative Extension, upon which the preceding discussion was based, with additions by the inventor.
Fly control is excellent in manure packs that have high numbers of Hister Beetles and Machrochelid Mites. The inventor has observed densities as high as 250 beetles per quart of manure, and 12 beetles per square inch of manure surface. Up to 20 mites per square inch of manure surface have been observed, as well.
A severe fly breakout normally occurs in 3-6 weeks after cleaning the manure out of a barn (about two fly generations). The problem with depending upon natural populations of predators to control these outbreaks is the slow rate of natural re-colonization after the periodic cleaning out of manure accumulations. Natural re-colonization can be very slow--on the nature of twelve or more weeks, if at all.
While some insects can be purchased from commercial breeders, the inventor has not been able to find the specific predators used here. In any event, purchasing predators can be expensive in the quantities needed. In the past, some farmers have transferred manure from one barn which has a mature predator population to the newly cleaned-out barn, or attempted to vacuum up the predators off mature manure piles. This is a very risky procedure due to the chance of cross-infection of poultry diseases carried by the manure, and also due to the spread of undesirable hide beetle and litter beetle pests along with the desirable predators.